A continuing goal of integrated circuit fabrication is to increase integration density. One approach used to achieve increased integration density involves reducing the lateral footprint of individual structures by increasing the aspect ratio (i.e., ratio of height to width or diameter) of the individual structures and the proximity of adjacent structures. However, one problem with this approach is that spaces between closely adjacent high aspect ratio (HAR) structures can act as capillaries during post-formation processes (e.g., “release-related” processes such as cleaning, rinsing, and drying, and “in-use” processes such as post-drying processes), such that liquid (e.g., water or other solvent) is drawn into such spaces. High surface tension forces resulting from the liquid in the spaces between adjacent HAR structures can cause the adjacent HAR structures to topple or collapse toward each other, bringing the adjacent HAR structures into contact with each other, as shown in FIG. 1. The gap between the adjacent HAR structures can produce surface forces (e.g., Van der Waals, electrostatic, hydrogen bonding, capillary, solid bridging, etc.) that cause the adjacent HAR structures to statically adhere to each other. Such static adhesion is commonly referred to in the art as “stiction.” Stiction between the adjacent HAR structures can substantially impede desired functions of a semiconductor device structure or even render the semiconductor device structure inoperable (e.g., by substantially damaging components of the semiconductor device structure).
The HAR structures may include features formed of a silicon-based material, such as silicon, silicon oxide, or silicon nitride. After forming the HAR structures, a wet chemistry is used to remove (e.g., clean) residues and to prepare the surface of the HAR structures for subsequent process acts. Various wet chemistries have been investigated to reduce the surface tension or increase a contact angle between the wet chemistry and the surface of the HAR structures. The wet chemistry is followed by drying to remove the wet chemistry. The drying of the HAR structures includes heating or using an isopropanol (IPA) rinse, which has a low surface tension. The HAR structures may be exposed to multiple wet chemistry and drying acts during the overall fabrication process.
Conventional methods of reducing toppling include rinsing the HAR structures with low surface tension liquids, such as isopropanol (IPA) or fluorinated organic surfactants, followed by drying with nitrogen (N2). While IPA is effective in reducing surface tension, the IPA does not increase the contact angle. Modifications of the surface of the HAR structures have also been investigated to reduce toppling. Hexamethyldisiloxane (HMDS) or fluorinated silanes have been bonded to the surface of the HAR structures to increase the contact angle. However, the resulting contact angles are less than 90°. Moreover, the surface modifications do not prevent collapse as the aspect ratio of the HAR structures increases above about 22:1.
A need, therefore, exists for developing additional compositions and methods of reducing toppling of adjacent HAR structures of a semiconductor device structure.